Electrical measuring instrument.



No. 636,097. Patented Oct. 3!, I899. V. ARCIONI.

ELECTRICAL MEASURING INSTRUMENT.

(Applicatioh filed. May 10, 1899.)

ZLU 6 711-07" Z' %W (No Model.)

section upon the line b bin said Fig. 2.

UNITED. STATES PATENT OFFICE.

VITTORIO ARCIONI, OF IVREA, ITALY, ASSIGNOR TO CAMILLO OLIVETTI, -OFSAME PLACE.

ELECTRICAL M EASUYRI'NVG INSTRU M ENT.

SPECIFICATION forming part of Letters Patent No. 636,097, dated October31, 1899.

' Application filed May 10, 1899. Serial No. 716,299. (No model.)

To all whom it may concern:

Be it known that LVITTORIO ARCIONI, a-subject of the King of Italy,residing at Ivrea,

Italy, have invented certain new and useful Improvements in ElectricalInstruments, of which the following is a specification.

My invention relates to that class or type of electrical measuringinstruments used to measure the potential in volts or the quantity inamperes of an electric current, either continuous 0 r alternating.

It is the purpose of my invention to provide a measuring instrument inwhich'the linear expansion of the wire conductor shall permita widerange of movement to theindex, means being used to multiply thevibrations, whereby it will extend over an are greater than that usuallycalibrated in the instruments heretofore used. I aim also to provide avoltmeter or ammeter which shall be capable of giving accurateindications under all circumstances and in which the calibrations aresubstantially uniform in all parts of the graduated scale.

My invention also comprises other novel features, which will be fullydescribed hereinafter and then particularly pointed out and defined inthe claims.

For the purposes of the following explanation reference is had to theaccompanying drawings, in which Figure 1 isan elevation showing theworking parts of a measuring instrument constructed in accordance withmy invention. Fig. 2 is a view showing the multiplying-arm removed fromits post with its spool for the conducting-wire. the same on the line aa, Fig. 2. Fig. 4t is a Fig. 5 is a cross-section of the multiplying-armon the line 0 c in Fig. 2.

The reference-letter A in said drawings indicates the casing of theinstrument, which is constructed in substantially the same manner asheretofore. It is provided with a calibrated plate a, over which thepoint of an index I has movement. This index has its axis at or near thepoint 0, where there is a small pulley P, having an eccentric axis. Thispulley carries the index I.

Supported on a post A is a thin flexible Fig. 3 is a detail section ofjection b, at a right angle to the surface of the plate A and upon theend thereof, at a short distance from the plate, is a spool B, arrangedhorizontally and parallel with the plate A Said spool hangs directlyover a second and similar spool D, which is placed not far from the axis0 and is mounted rigidly upon the casing. Both spools are of anysuitable insulating material.

The letters T and T indicate the terminals of the instrument. The wirecarrying the current is indicated by F, and it is led from the terminalT under the spool D, which has a series of circumferential grooves toreceive said wire, and thence it is carried upward over the spool B,then down under the spool D in the next groove of the same, and so on,passing over the upper spool B and under the lower spool D until all thegrooves are filled. The end of the wire is then led to the secondterminal T andfastened. This arrangement provides a series of parallelstrands of wire f f tremity of said arm toward the'right hand in Fig. 1or away from the axis 0 and pulley P. Said end 0 of themultiplying-arm'is connected by a light flexible wire 0 to the pulley P,upon the circumference of which it is wound and fastened to preventslipping. On said pulley a similar wire m is attached in like manner,save that it is wound in the opposite direction, and its end is securedto the end of a leaf-spring M, which lies substan tially on a level withthe end 0 of the arm, the other end of said spring being rigidly mountedin a post M, projecting from the casing. The tension of this spring isso adjusted that it does not quite equal the strain of the wire strandsf when the latter are at normal temperature, whereby the latter willwhen there is no current passing throw the index I over to zero, as seenin Fig. l. \Vhen current is flowing over the wire F, the heat producedtherein and the resulting expansion of the wire diminish the strainbetween the spools B and D, so that the spring M is able to overcome theforce tending to carry the end 0 of the arm A away from the pulley I Thelatter, therefore, will be turned by the pull of the spring M upon thewire m, and the point of the index I will be moved over the calibratedplate a space proportionate to the degree of heat developed in the wireby the current.

The pulley P is on an eccentric axis 0 in order that the successivedisplacements of the index I may be uniform in extent, thus avoiding thenecessity of increasing the divisions of the calibrated glate.

A set-screw R is tapped through a post B, so that the point of the screwwill bear against the spring M at a point suitably near the post M. Thisscrew is used to set the point of the index I accurately at zero on thecalibrated plate, and in packing the instrument for transportation saidscrew can be so manipulated that the index will be drawn against thestud K, which will alTord a support for it during transit.

To prevent variations of temperature of the external atmosphere fromdestroying the accuracy of the indications of the instrument, the casinghas such a coefficient of thermal expansion that when the temperaturerises or falls the part between the points D and A expands or contractsequally with the part of the multiplying-arm between the points B and Aplus the length of the wire between D and B.

When used to measure potential, as a voltmeter, the strands f f of wireshould be numerous and of small diameter, with the strain equallydivided between the strands.

When used to measure the current in amperes, the wire F will be ofgreater diameter, and as it will have more tensile strength the numberof strands ffoan be diminished, and in certain cases a single strandonly will be required. The spools B and D may then be dispensed with andthe wire joined directly to the two points where said spools are locatedin any suitable manner.

To increase its flexibility and to locate the point where the flexionwill mainly take place, I form small punctures or openings at n in theplate A It is desirable that the flexibility shall be wholly or mainlylocated in this plate and not in the arm, which is stiffened, as alreadydescribed, by being made angular in cross-section.

WVhat I claim as my invention, and desire to secure by Letters Patent ofthe United States, is

- 1. An electrical measuring instrument having an index movable over acalibrated plate, a spring acting upon said index in one direction, amultiplying-arm supported rigidly at one end and having its other endconnected to the index to counteract the action of the spring, and awire connecting the terminals of the instrument and secured to insulatedpoints between said terminals, one point being on the multiplying-armnear the point of support of the latter, and the other insulatingpointbeing rigid on the case near the axis of the index, substantially asdescribed.

2. In an electrical measuring instrument, for indicating the potential,or the quantity of electric currents, the combination with an indexmovable over a calibrated plate, of a spring acting on said index in onedirection, a n1 ultiplying-arm hanging from a post in the casing andhaving its lower end connected to the index to counteract the spring,and a wire connecting the terminals of the instrument and secured toinsulated points between said terminals, one point being a spool formingpart of a projection on the multiplying-arm near its support and a spoolon the casing, near the lower end of the arm, substantially asdescribed.

3. In an electrical measuring instrument, the combination with an indexwhich is movable over a calibrated plate, of a spring to move said indexin one direction, a multiplying-arm which is flexible at one end andrigidly mounted by said end, in a post, the other end of said arm beingconnected to the index to counteract the spring, and a wire connected toone of the terminals of the instrument and carried thence under a rigidspool, then over a second spool rigidly mounted on the multiplying-armthen under the first spool, and, after a suitable number of turns onsaid spools, to the second terminal, substantially as described.

4. In an electrical measuring instrument, the combination with an indexwhich is movable over a calibrated surface, of a spring acting on saidindex to produce movement in one direction, a multiplying-arm which isflexible at one end which is provided with a series of punctures, saidend being rigidly mounted in a post from which said arm hangs downward,its lower end being connected to the index to counteract the spring,anda wire wound over an insulated spool mounted on a projection fromsaid multiplying-arm at or near a point between its flexible end andrigid body portion, then under a like spool rigidly attached to asupport near the lower end of said multiplying-arm, the ends of saidwire being connected to the terminals of the instrument and the strandsbetween the two spools being of a number suited to the measurementsindicated by the instrument and maintained under tension at normaltemperatures, substantially as described.

5. In an electrical measuring instrument,- the combination with anindex, of an eccentric pulley on which one end of said index is mounted,a spring having its end connected by a flexible wire to said pulley, amultiplying-arm hanging from a post in the upper part of the casing, itslower end being connected by a flexible wire to the eccentric pulley tocounteract the action of the spring, and a wire wound over and under twogrooved, insulated spools, one forming part of a projection from themultiplying-arm near its supported end, and the other being rigidlyfixed in the casing near the lower end of said arm, the ends of saidwire being secured to the terminals of the instrument, substantially asdescribed.

6. In an electrical measuring instrument, the combination with anindex,of aleaf-spring having one end fixed in a post and the other endconnected to said index, a multiplyingarm hanging from a post and havingits lower hand in presence of two subscribing wit-' nesses.

VITTORIO ARCIONI.

Witnesses FUMENE ERNES'IE, ENRIco MARANA.

